X-ray & Optical Images of Delta Orionis
Delta Orionis is a complex star system that contains five stars in total. Two of those stars are in a close orbit where one passes in front of another from the vantage point of Earth, which helps astronomers learn more about their properties. The massive stars in this pair are so bright that their radiation blows powerful winds of stellar material away, affecting the chemical and physical properties of the gas in their host galaxies. Astronomers observed this system for the equivalent of nearly six days with Chandra to better understand these relatively rare but important stars.
(Credit: X-ray: NASA/CXC/GSFC/M.Corcoran et al.; Optical: Eckhard Slawik)

Illustration of Delta Orionis
This artist's illustration depicts the system of Delta Orionis A. In the center, two closely separated stars orbit around each other every 5.7 days and this pair is known as Delta Orionis Aa. The more massive, or primary, star in Delta Orionis Aa weighs about 25 times the mass of the Sun, whereas the less massive, or secondary star, weighs about ten times the mass of the Sun. The chance alignment of this pair of stars allows one star to pass in front of the other during every orbit from the vantage point of Earth. This special class of star system is known as an "eclipsing binary," and it gives astronomers a direct way to measure the mass and size of the stars. Meanwhile a third star, dubbed Delta Orionis Ab, orbits the eclipsing binary with a period of over 400 years.
(Credit: NASA/CXC/M.Weiss)